It is a pleasure to acknowledge the stimulus and suggestions provided over many
years by Donald Michie, who continues to play a central role in the development of
this methodology. Ivan Bratko, Igor Kononenko, Igor Mosetic and other members
of Bratko's group have also been responsible for many insights and constructive
criticisms. I have benefited from numerous discussions with Ryszard Michalski, Alen
Shapiro, Jason Catlett and other colleagues. I am particularly grateful to Pat Langley
for his careful reading of the paper in draft form and for the many improvements
he recommended.